1. Technical Field
The invention relates to differential encoders with self-adaptive predictive filter and it is particularly, although not exclusively, suitable for use in the telephone field where it is desirable to have both good speech reproduction quality for the lowest possible in-line bit rate (for example 16 kbits/s) and a high resistance to transmission errors.
2. Prior Art
different encoders are already known which operate at the above bit rate, particularly vocoders with impulse energization and sub-band encoders. These encoders are complex. In addition, they introduce delays of several tens of milliseconds. An ADPCM encoder is also known (FR-A-2,445,660) having a predictive filter and an analyzing filter, consequently complex in construction.